HDP Reactors: Conclusions

Plasma source: Specialized plasma sources (ECR, inductive) are required to provide sufficiently dense plasmas; simple diode reactors cannot be used. Independent control of ion energy and density results.
Temperature control: Large heat loads to the wafer from RF bias must be dissipated by backside gas, forcing use of complex clamping and chuck arrangements.

Uniformity: Transport is mixed, with significant diffusion assisting uniform deposition; design of gas dispenser is complicated by near-Knudsen local transport, contamination and erosion concerns.

Cost: Reactors require large-area dielectric walls, very high pumping speeds, dual power supplies and matching networks, sophisticated wafer chucks: the reactor chambers are expensive.

Productivity advantages: Films are dense as deposited, avoiding the requirement for post-deposition anneals at high temperature. Single-step planarization is achieved, so a separate polishing step may not be needed.

Productivity disadvantages: Requirement for filling high aspect ratio features (high sputter rate) reduces throughput. High deposition rates require expensive high power RF supplies.

Process advantages: Dense films are stable against ambient exposure without post-deposition anneal, and integrate smoothly with chemical mechanical polishing (CMP) planarization.

Process disadvantages: Sputtering can damage underlying structures at process turnon. Plasma damage can result if strong DC magnetic fields are employed.

HDP reactors are relatively expensive and complex to fabricate and maintain. However, they have the unique ability to deposit silicon dioxide which is comparable in density to thermal oxide without exposing the wafer to very high temperatures, and good gap fill and local planarization. Key applications are in intermetal dielectric deposition, and trench fill for shallow trench isolation (STI).

- - - - - - - - -

other HDP references:

"High Density Plasma Etch Induced Damage to Thin Gate Oxide" S. Krishnan, S. Aur, G. Wilhite and R. Rajgopal, IEDM 1995 p. 315
"Charge separation in an electron cyclotron resonance plasma" M. Inoue and S. Nakamura, J. Vac. Sci. Technol. A13 327 (1995)
"Implementation of Electron Cyclotron Resonance Plasma SiO2 into Sub-half Micron Technology" C. Wang, Y. Huang, D. Pirkle, L. Liu, J. Wang, H. Cheng and M. Lin, DUMIC 1995 p. 29
"Control of Plasma Damage to Gate Oxide during High Density Plasma Chemical Vapor Deposition" S. Bothra, C. Gabriel, S. Lassig and D. Pirkle, J. Electrochem. Soc. 142 L208 (1995)
"Assessment of charge-induced damage from High Density Plasma (HDP) Oxide Deposition", S. Krishnan and S. Nag, First International Symposium on Plasma Process-Induced Damage, May 13-14 1996, Santa Clara, CA p. 67
"Silicon nitride growth in a high-density plasma system" C. Apblett, M. Gonzales, C. Barbour, L. Gonzales-Peterson, M. Kovacs, B. Kuhr, Solid State Technology November 1995 p.73

Return to Tutorial Table of Contents
Book version of the CVD Tutorial